Field of the Invention
The present disclosure relates, in general, to empty/load valves for railway vehicles and, in particular, to a brake cylinder pressure adjustment feature for empty/load valves.
Description of Related Art
Brake equipment for railway freight cars typically employs dual capacity empty/load equipment that adjusts the brake application force according to the empty or loaded conditions of the freight car. In such dual capacity empty/load equipment, a two-setting control is provided where normal brake pressure is realized under full load conditions and a reduced or modulated brake pressure is realized under an empty load condition. In contrast, single capacity brake equipment, which produces a brake application force independent from the load condition of the car loading, is susceptible to wheel lock and sliding wheels due to the same brake force being applied to an empty car as a loaded car. Sliding wheels undesirably cause flat spots on the wheels as well as decreased brake performance. By modulating the brake pressure under empty load conditions using dual capacity empty/load equipment, the occurrence of sliding wheels is reduced or eliminated. Typically, the changeover point between the empty and load settings is selected at a predetermined car weight, such as 20% of the full load capacity weight. When freight cars are either fully loaded or completely empty, the dual capacity empty/load equipment generally functions acceptably. However, with varying load conditions, i.e., loads that are intermediate a full load and an empty condition, dual capacity empty/load equipment may not be satisfactory as cars having a partial load may be under-braked or over-braked depending on the pre-selected changeover point between the empty and load settings.
Current empty/load equipment is preset by the manufacturer and is not adjustable by the operator in the field. Since a complete disassembly of the empty/load equipment is necessary to adjust a slotted beam press or fulcrum within the empty/load equipment, the settings are preset at the manufacturing facility. Therefore, the operator is unable to adjust the settings according to his/her specific freight car when in the field. Current empty/load equipment may also include a continuous adjustment feature to adjust the settings on the empty/load equipment. However, without a setting indicator on the empty/load equipment, the set air pressure for the empty/load equipment is often unknown without supplying pressurized air to the empty/load equipment.